Anyone know how I can create a cronjob for data (specific accounts) backup via cpanel/whm? I want to backup certain accounts on my second mounted drive but not sure how to do this. I need this done daily via cronjob.

cPanel doesnt give you the option to backup specific accounts via it's backup manager. If you wanted to do this you could but you will need to either add this line to your crontab for each user or create a file with them all in it and throw that in your crontab.

/scripts/pkgacct <username> <location-to-put-backup> backup

so for example you have the user joeblow and wanted to put his files in /var/backup the syntax would be

/scripts/pkgacct joeblow /var/backup backup